There is much evidence that carbohydrates are involved in many cell surface mediated processes. A model system has, therefore, been developed to study cell interactions with carbohydrate molecules immobilized on a chemically defined flat polyacrylamide surface. Conditions suitable for cell attachment and growth can be achieved by accurately controlling the type and concentration of molecules on the synthetic surface. I will examine the interaction of many types of primary and established cells with external carbohydrate molecules of varying complexity from simple synthetic monosaccharide derivatives to large glycosaminoglycans. Cellular responses will be determined by measuring parameters such as cell binding, spreading, growth rate, saturation density, morphology, migration and contact inhibition of motion and growth. Different cell responses may occur in the presence of various external carbohydrates. Special attention will be given to studies on growth control and cell motility since preliminary evidence suggests that simian virus 40 transformed Balb/c 3T3 cells will grow on a particular carbohydrate surface, whereas the non-transformed Balb/c 3T3 cells will not. Possible correlations between the behavioral difference on carbohydrate surfaces and transformation will be examined in these and other, cell lines. Use of this model system recently led to the discovery that the specific binding of rat and chicken hepatocytes to a carbohydrate surface is a threshold response. Cell binding only occurs to surfaces that contain glycoside levels above a critical concentration. The molecular basis for the threshold binding response of rat hepatocytes to galactose surfaces will be determined.